The best option for this is FTP (File Transfer Protocol). You can find many free applications for FTP at http://www.download.com/.

FTP gives you the ability to transfer files from your computer to the server. So you can write your web pages in an HTML editor such as Frontpage, Notepad, or dreamweaver. Then using FTP, you can upload them directly to the server into the httpdocs directory (Plesk), or the public_html directory (CPanel)

Your "Welcome Email" that you received when signing up has all the information needed to login using FTP.